Both child and adult probands are being used to identify families segregating an obese phenotype. Lymphoblastoid cell lines are being prepared on members of pedigrees, creating a genetic resource in perpetuity. Tests for allelic association (linkage disequilibrium) affected sib-pair and genetic linkage analysis are being performed. Ultimately, this genetic resource can also be used to search for loci linked to specific aspects of phenotype using linked clones spanning the genome.